Method for shaping spring elements

ABSTRACT

Interconnection elements for electronic components, exhibiting desirable mechanical characteristics (such as resiliency, for making pressure contacts) are formed by using a shaping tool ( 512 ) to shape an elongate core element ( 502 ) of a soft material (such as gold or soft copper wire) to have a springable shape (including cantilever beam, S-shape, U-shape), and overcoating the shaped core element with a hard material (such as nickel and its alloys), to impart a desired spring (resilient) characteristic to the resulting composite interconnection element. A final overcoat of a material having superior electrical qualities (e.g., electrical conductivity and/or solderability) may be applied to the composite interconnection element. The resulting interconnection elements may be mounted to a variety of electronic components, including directly to semiconductor dies and wafers (in which case the overcoat material anchors the composite interconnection element to a terminal (or the like) on the electronic component), may be mounted to support substrates for use as interposers and may be mounted to substrates for use as probe cards or probe card inserts. The shaping tool may be an anvil ( 622 ) and a die ( 624 ), and may nick or sever successive shaped portions of the elongate element, and the elongate element may be of an inherently hard (springy) material. Methods of fabricating interconnection elements on sacrificial substrates are described. Methods of fabricating tip structures ( 258 ) and contact tips at the end of interconnection elements are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of PCT InternationalApplication Serial No. US96/08276 which was filed on May 28, 1996 anddesignated the United States. This patent application is based onProvisional U.S. Application Serial No. 60/013,247 which was filed onMar. 11, 1996. This patent application is a continuation-in-part ofcommonly-owned, U.S. patent application Ser. No. 08/452,255 (hereinafter“PARENT CASE”) filed May 26, 1995 and its counterpart PCT patentapplication Ser. No. PCT/US95/14909 filed Nov. 13, 1995, both of whichare continuations-in-part of commonly-owned, U.S. patent applicationSer. No. 08/340,144 filed Nov. 15, 1994 and U.S. Pat. No. 5,917,707,issued Jun. 29, 1999 now its counterpart PCT patent application numberPCT/US94/13373 filed Nov. 16, 1994 (published May 26, 1995 as WO95/14314, both of which are continuations-in-part of commonly-owned,U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (nowU.S. Pat. No. 5,476,211, Dec. 19, 1995), all of which are incorporatedby reference herein.

This patent application is also a continuation-in-part of U.S.application Ser. No. 08/570,230 which was filed on Dec. 11, 1995, nowU.S. Pat. No. 5,852,871, issued Dec. 29, 1999 and U.S. application Ser.No. 08/457,479 which was filed on Jun. 1, 1995, now U.S. Pat. No.6,044,976, issued Apr. 18, 2000 both of which are divisionals of U.S.application Ser. No. 08/152,812 which was filed on Nov. 16, 1993 (nowU.S. Pat. No. 5,476,211 issued on Dec. 19, 1995).

This patent application is also a continuation-in-part of the followingcommonly-owned, U.S. patent application Ser. Nos.:

08/526,246 filed Sep. 21, 1995 (PCT/US95/14842, Nov. 13, 1995);

08/533,584 filed Oct. 18, 1995 now U.S. Pat. No. 5,772,451, issued Jun.30, 1998 (PCT/US95/14843, Nov. 13, 1995);

08/554,902 filed Nov. 9, 1995 now U.S. Pat. No. 5,974,662, issued Nov.2, 1999, (PCT/US95/14844, Nov. 13, 1995);

08/558,332 filed Nov. 15, 1995 now U.S. Pat. No. 5,829,128, issued Nov.3, 1998, (PCT/US95/14885, Nov. 15, 1995);

08/573,945 filed Dec. 18, 1995; now U.S. Pat. No. 5,601,740 issued Feb.11, 1997

08/584,981 filed Jan. 11, 1996; now U.S. Pat. No. 5,820,014, issued Oct.13, 1998,

08/602,179 filed Feb. 15, 1996; now abandoned,

60/012,027 filed Feb. 21, 1996;

60/012,040 filed Feb. 22, 1996;

60/012,878 filed Mar. 5, 1996; and

60,005,189 filed May 17, 1996

all of which, except for the Provisional cases, arecontinuations-in-part of the aforementioned PARENT CASE, and all ofwhich are incorporated by reference herein.

TECHNICAL FIELD OF THE INVENTION

The invention relates to shaping bond wires, particularly free-standingbond wires used as core elements for composite interconnection elementsuch as are described in commonly-owned, copending U.S. patentapplication Ser. No. 08/452,255 filed May 26, 1995 (status: pending) andits counterpart PCT patent application number PCT/US95/14909 filed Nov.13, 1995.

BACKGROUND OF THE INVENTION

Electronic components, particularly microelectronic components such assemiconductor devices (chips), often have a plurality of terminals (alsoreferred to as bond pads, electrodes, or conductive areas). In order toassemble such devices into a useful system (or subsystem), a number ofindividual devices must be electrically interconnected with one another,typically through the intermediary of a printed circuit (or wiring)board (PCB, PWB).

Generally, interconnections between electronic components can beclassified into the two broad categories of “relatively permanent” and“readily demountable”.

An example of a “relatively permanent” connection is a solder joint.Once two electronic components are soldered to one another, a process ofunsoldering must be used to separate the components. A wire bond isanother example of a “relatively permanent” connection.

An example of a “readily demountable” connection is rigid pins of oneelectronic component being received by resilient socket elements ofanother electronic component. The socket elements exert a contact force(pressure) on the pins in an amount sufficient to ensure a reliableelectrical connection therebetween. Interconnection elements intended tomake pressure contact with an electronic component are referred toherein as “springs” or “spring elements” of “spring contacts”.

Prior art techniques for making spring contact elements generallyinvolve stamping (punching) or etching a “monolithic” spring material,such as phosphor bronze or beryllium copper or steel or anickel-iron-cobalt (e.g., kovar) alloy, to form individual springelements, shaping the spring elements to have a spring shape (e.g.,arcuate, etc.), plating the spring elements with a good contact material(e.g., a noble metal such as gold, which will exhibit low contactresistance when contacting a like material), and molding a plurality ofsuch shaped, plated spring elements into a linear, a peripheral or anarray pattern. When plating gold onto the aforementioned materials,sometimes a thin (for example, 30-50 microinches, barrier layer ofnickel is appropriate.

Generally, a certain minimum contact force is desired to effect reliablepressure contact to electronic components (e.g., to terminals onelectronic components). For example, a contact (load) force ofapproximately 15 grams (including as little as 2 grams or less and asmuch as 150 grams or more, per contact) may be desired to ensure that areliable electrical connection is made to a terminal of an electroniccomponent which may be contaminated with films on its surface, or whichhas corrosion or oxidation products on its surface. The minimum contactforce required of each spring element typically demands either that theyield strength of the spring material or that the size of the springelement are increased. However, generally, the higher the yield strengthof a material, the more difficult it will be to work with (e.g., punch,bend, etc.). And the desire to make springs smaller essentially rulesout making them larger in cross-section.

In commonly-owned, copending U.S. patent application Ser. No. 08/452,255filed May 26, 1995 (and its counterpart PCT/US95/14909 filed Nov. 13,1995), techniques are described for shaping elongate core elements (wirestems) of composite interconnection elements using a wirebonder. A oneend of a supply wire is ball-bonded to an area (e.g., terminal) on asubstrate (e.g., electronic component) by urging a capillary of awirebonder downward (z-axis) onto the substrate. The capillary is thenwithdrawn (upward), and as the wire plays (feeds) out of the capillary,the substrate is moved in the x-y plane to impart a desired spring shapeto the portion of the wire between the substrate and the capillary. Thewire is then severed adjacent the capillary, resulting in afree-standing wire stem which is mounted to the substrate. Thepossibility of using external, mechanical instrumentalities to impartthe desired shape to the wire stem is discussed, and is elaborated uponherein.

The following U.S. Patents are cited as being of interest: 5,386,344;5,336,380; 5,317,479; 5,086,337; 5,067,007; 4,989,069; 4,893,172;4,793,814; 4,777,564; 4,764,848; 4,667,219; 4,642,889; 4,330,165;4,295,700; 4,067,104; 3,795,037; 3,616,532; and 3,509,270.

Attention if also directed to U.S. Pat. No. 5,045,975 issued Sep. 03,1991, entitled THREE-DIMENSIONALLY INTERCONNECTED MODULE ASSEMBLY, whichdiscloses ball bonding a plurality of gold wires (leads) onto andsubstantially perpendicular to an integrated circuit die, and insertingthe gold leads into plated through holes of printed circuit boards toeffect an electrical and mechanical connection therebetween. Thetechnique is also useful for interconnecting sandwiched assemblies ofcircuit boards. This patent illustrates the feasibility of adding anotching mechanism to a wirebonder (ball bonder), and also illustratesthe technique.

BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION

It is an object of the invention to provide an improved technique forshaping core elements of a composite interconnection element to have anappropriate spring shape.

It is another an object of the invention to provide a technique forfabricating resilient interconnection elements (contact structures) forelectronic components, particularly for microelectronic components.

It is another object of the invention to provide resilient contactstructures (interconnection elements) that are suitable for makingpressure contact to electronic components.

It is another object of the invention to provide a technique forsecurely anchoring interconnection elements to electronic components.

According to the invention, an external mechanical instrumentality(shaping tool) is used to impart a desired shape to portion of anelongate element (e.g., a bond wire).

In an embodiment of the invention, the shaping tool is a one-part tool,which urges (pushes) against a portion of the bond wire extendingbetween an area (e.g., terminal) on a substrate (e.g., electroniccomponent, sacrificial substrate, etc.) and a capillary of a wirebonder.

In another embodiment of the invention, the shaping tool is a two-parttool, comprising an anvil and a die. The anvil and die are broughttogether, with the elongate element (e.g., wire) therebetween, to impartthe desired shape to the elongate element.

According to an aspect of the invention, the shaping tool is providedwith a feature which can nick or completely sever the elongate elementwhile performing shaping.

According to an aspect of the invention, the shaping tool can be biased(at an electrical potential, including ground) to control a spark(electrical discharge) which is used to sever the elongate element.

According to another aspect of the invention, regions of reduceddiameter formed by the shaping tool can “attract” a spark duringspark-severing (e.g., from an EFO electrode).

The present invention is particularly useful for, but is not limited to,shaping core elements of composite interconnection elements, which arefabricated by bonding a one end of a bond wire to a terminal on anelectronic component (or to an area of a sacrificial substrate),imparting a spring shape to the wire, and severing the wire to be afree-standing wire stem (core element). The free-standing wire stem isovercoated with one or more layers of material to impart a desiredresiliency and, optionally, electrical contact characteristics to theresulting composite interconnection element. It is within the scope ofthis invention that the core element is other than a wire having acircular cross-section. For example, the core element may have arectangular cross-section and be in the form of a “ribbon”.

The disclosed techniques overcome problems associated with making springelements of extremely small size, yet which are capable of exertingcontact forces of sufficient magnitude to ensure reliableinterconnections. The disclosed techniques also overcome problemsassociated with mounting spring contacts directly on various electroniccomponents, such as semiconductor devices.

The use of the term “composite”, throughout the description set forthherein, is consistent with a ‘generic’ meaning of the term (e.g., formedof two or more elements), and is not to be confused with any usage ofthe term “composite” in other fields of endeavor, for example, as it maybe applied to materials such as glass, carbon or other fibers supportedin a matrix of resin or the like.

As used herein, the term “spring shape” refers to virtually any shape ofan elongate element which will exhibit elastic (restorative) movement ofan end (tip) of the elongate element with respect to a force applied tothe tip. This includes elongate elements shaped to have one or morebends, as well as substantially straight elongate elements.

As used herein, the terms “contact area”, “terminal”, “pad”, and thelike refer to any conductive area on any electronic component (includingpassive substrates and sacrificial substrates) to which aninterconnection element is mounted or makes contact.

Generally, the core is a “soft” material having a relatively low yieldstrength, and is overcoated with a “hard” material having a relativelyhigh yield strength. For example, a soft material such as a gold wire isattached (e.g., by wire bonding) to a terminal of an electroniccomponent, and is overcoated (e.g., by electrochemical plating) with ahard material such nickel and its alloys.

Generally, throughout the description set forth herein, the term“plating” is used as exemplary of a number of techniques for overcoatingthe core element. It is within the scope of this invention that the coreelement can be overcoated by any suitable technique including, but notlimited to: various processes involving deposition of materials out ofaqueous solutions; electrolytic plating; electroless plating; chemicalvapor deposition (CVD); physical vapor deposition (PVD); processescausing the deposition of materials through induced disintegration ofliquid or solid precursors; and the like, all of these techniques fordepositing materials being generally well known.

Generally, for overcoating the core element with a metallic materialsuch as nickel, electrochemical processes are preferred, especiallyelectrolytic plating.

Representative materials, both for the core element and for theovercoating, are disclosed.

In the main hereinafter, techniques involving beginning with arelatively soft (low yield strength) core element, which is generally ofvery small dimension (e.g., 3.0 mil or less) are described. Softmaterials, such as gold, which attach easily to the metallization (e.g.,aluminum) of semiconductor devices, generally lack sufficient resiliencyto function as springs. (Such soft, metallic materials exhibit primarilyplastic, rather than elastic deformation.) Other soft materials whichmay attach easily to semiconductor devices and possess appropriateresiliency are often electrically non-conductive, as in the case of mostelastomeric materials. In either case, desired structural and electricalcharacteristics can be imparted to the resulting compositeinterconnection element by the overcoating applied over the core. Theresulting composite interconnection element can be made very small, yetcan exhibit appropriate contact forces. Moreover, a plurality of suchcomposite interconnection elements can be arranged at a fine pitch(e.g., 10 mils), even though the have a length (e.g., 100 mils) which ismuch greater than the distance to a neighboring compositeinterconnection element (the distance between neighboringinterconnection elements being termed “pitch”).

It is within the scope of this invention that composite interconnectionelements can be fabricated on a microminiature scale, for example as“microsprings” for connectors and sockets, having cross-sectionaldimensions on the order of twenty-five microns (μm), or less. Thisability to manufacture reliable interconnection having dimensionsmeasured in microns, rather than mils, squarely addresses the evolvingneeds of existing interconnection technology and future area arraytechnology.

The composite interconnection elements of the invention exhibit superiorelectrical characteristics, including electrical conductivity,solderability and low contact resistance. In many cases, deflection ofthe interconnection element in response to applied contact forcesresults in a “wiping” contact, which helps ensure that z reliablecontact is made.

An additional advantage of the invention is that connections made withthe interconnection elements of the invention are readily demountable.Soldering, to effect the interconnection to a terminal of an electroniccomponent is optional, but is generally not preferred at a system level.

According to an aspect of the invention, interconnection elements can bepre-fabricated as individual units, for later attachment to electroniccomponents. Various techniques for accomplishing this objective are setforth herein. Although not specifically covered in this document, it isdeemed to be relatively straightforward to fabricate a machine that willhandle the mounting of a plurality of individual interconnectionelements to a substrate or, alternatively, suspending a plurality ofindividual interconnection elements in an elastomer, or on a supportsubstrate.

It should clearly be understood that the composite interconnectionelement of the invention differs dramatically from interconnectionelements of the prior art which have been coated to enhance theirelectrical conductivity characteristics or to enhance their resistanceto corrosion.

In addition to controlling the resiliency of the resulting compositeinterconnection element, the overcoating substantially enhancesanchoring of the interconnection element to a terminal of an electroniccomponent. Stresses (contact forces) are directed to portions of theinterconnections elements which are specifically intended to absorb thestresses.

One advantage of the invention is that the processes described hereinare well-suited to “pre-fabricating” interconnection elements,particularly resilient interconnection elements, such as on asacrificial member, then later mounting the interconnection elements toan electronic component. In contrast to fabricating the interconnectionelements directly on the electronic component, this allows for reducedcycle time in processing the electronic components. Additionally, yieldissues which may be associated with the fabrication of theinterconnection elements are thus disassociated from the electroniccomponent. For example, it would be disingenuous for an otherwiseperfectly good, relatively expensive integrated circuit device to beruined by glitches in the process of fabricating interconnectionelements mounted thereto. The mounting of pre-fabricated interconnectionelements to electronic components is relatively straightforward, as isevident from the description set forth hereinbelow.

It should also be appreciated that the invention provides essentially anew technique for making spring structures. Generally, the operativestructure of the resulting spring is a product of plating, rather thanof bending and shaping. This opens the door to using a wide variety ofmaterials to establish the spring shape, and a variety of “friendly”processes for attaching the “falsework” of the core to electroniccomponents. The overcoating functions as a “superstructure” over the“falsework” of the core, both of which terms have their origins in thefield of civil engineering.

One of the significant advantages of using a readily-deformable,malleable, compliant material for the wire stem is that it is readilyconfigured to establish a shape for the overcoat applied thereto,without significantly altering the physical properties (e.g., tensilestrength, resiliency, etc.) of the resulting resilient contactstructure. Inasmuch as the wire stem serves as an important first stepin the overall process (begun, but not completed) of fabricating aresulting contact structure, the wire stem can be characterized as an“inchoate” contact structure.

The composite interconnection (spring) elements of the invention areapplicable to a broad range of applications, for example, for use ininterposers. The subject of using composite interconnection elements ininterposers has been discussed in the PARENT CASE. Generally, as usedherein, an “interposer” is a substrate having contacts on two oppositesurfaces thereof, disposed between two electronic components tointerconnect the two electronic components. Often, it is desirable thatthe interposer permit at least one of the two interconnected electroniccomponents to be removed (e.g., for replacement, upgrading, and thelike).

The invention differs dramatically from the prior art in that anovercoat is used to impart desired mechanical characteristics (e.g.,elasticity) to an otherwise non-elastic, readily-formed, inchoateinterconnection element (contact structure). In the prior art, coatings(including gold platings) are principally used to enhance electricalcharacteristics of interconnection elements, and to prevent corrosionthereof.

The composite interconnection elements can either be fabricated“in-situ” on electronic components, or “pre-fabricated” for latermounting to electronic components.

Among the advantages of using a shaping tool to impart a desired shapeto a portion of an elongate element (e.g., wire), versus imparting theshape by moving the component relative to the capillary (or vice-versa),are:

problems with springback are largely avoided;

the desired shape can be developed more quickly;

a plurality of shaped portions of elongate elements can be produced in amore reproducible manner;

more positive control over the shape of the shaped portions of theelongate elements can be achieved; and

a plurality of free-standing, shaped wires can be mounted closer to oneanother on a substrate.

In instances wherein it is desired to shape and mount free-standingelongate elements to substrates, each free-standing elongate elementhaving its own orientation, the shaping tool can be provided withsufficient degrees of freedom to accommodate the various orientations.

For shaping relatively hard materials, such as may be used formonolithic interconnection elements or hard cores of compositeinterconnection elements, a shaping tool may be particularly useful, andmay be preferred.

Other objects, features and advantages of the invention will becomeapparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Although the invention will be described in the context ofthese preferred embodiments, it should be understood that it is notintended to limit the spirit and scope of the invention to theseparticular embodiments.

In the side views presented herein, often portions of the side view arepresented in cross-section, for illustrative clarity. For example, inmany of the views, the wire stem is shown full, as a bold line, whilethe overcoat is shown in true cross-section (often withoutcrosshatching).

In the figures presented herein, the size of certain elements are oftenexaggerated (not to scale, vis-a-vis other elements in the figure), forillustrative clarity.

FIG. 1A is a cross-sectional view of a longitudinal portion, includingone end, of an interconnection element, according to an embodiment ofthe invention.

FIG. 1B is a cross-sectional view of a longitudinal portion, includingone end, of an interconnection element, according to another embodimentof the invention.

FIG. 1C is a cross-sectional view of a longitudinal portion, includingone end of an interconnection element, according to another embodimentof the invention.

FIG. 1D is a cross-sectional view of a longitudinal portion, includingone end of an interconnection element, according to another embodimentof the invention.

FIG. 1E is a cross-sectional view of a longitudinal portion, includingone end of an interconnection element, according to another embodimentof the invention.

FIG. 2A is a cross-sectional view of an interconnection element mountedto a terminal of an electronic component and having a multi-layeredshell, according to the invention.

FIG. 2B is a cross-sectional view of an interconnection element having amulti-layered shell, wherein an intermediate layer is of a dielectricmaterial, according to the invention.

FIG. 2C is a perspective view of a plurality of interconnection elementsmounted to an electronic component (e.g., a probe card insert),according to the invention.

FIG. 2D is a cross-sectional view of an exemplary first step of atechnique for manufacturing interconnection elements, according to theinvention.

FIG. 2E is a cross-sectional view of an exemplary further step of thetechnique of FIG. 2D for manufacturing interconnection elements,according to the invention.

FIG. 2F is a cross-sectional view of an exemplary further step of thetechnique of FIG. 2E for manufacturing interconnection elements,according to the invention.

FIG. 2G is a cross-sectional view of an exemplary plurality ofindividual interconnection elements fabricated according to thetechnique of FIGS. 2D-2F, according to the invention.

FIG. 2H is a cross-sectional view of an exemplary plurality ofinterconnection elements fabricated according to the technique of FIGS.2D-2F, and associated in a prescribed spatial relationship with oneanother, according to the invention.

FIG. 2I is a cross-sectional view of an alternate embodiment formanufacturing interconnection elements, showing a one end of oneelement, according to the invention.

FIG. 3 is a partially-perspective, partially-schematic view ofwirebonding apparatus mounting a wire stem to a substrate (e.g.,electronic component), according to the invention. In this embodiment,the wire stem is shaped by relative movement between the capillary ofthe wirebonder and the substrate to which the wire stem is bonded.

FIG. 4A is a perspective view of operative portions of a wirebondingapparatus mounting a wire stem to a substrate (e.g., electroniccomponent), according to the present invention. In this embodiment, thewire stem will be shaped by an external shaping tool which is urgedagainst the wire stem.

FIG. 4B is a side view of the wirebonding apparatus of FIG. 4Aillustrating the technique of shaping the wire stem by means of theexternal shaping tool and, in conjunction with shaping the wire stem,severing the wire stem to be free-standing, according to the presentinvention.

FIG. 4C is a side view of the wirebonding apparatus of FIG. 4B,illustrating a fully-formed wire stem, and a ball having been formed atthe end of the supply wire for making subsequent wire bonds, accordingto the present invention.

FIG. 5A is a perspective view of wirebonding apparatus, including anembodiment of an external shaping tool, according to the invention.

FIGS. 5B and 5C are side views of a method of shaping an elongateelement (e.g., wire) with the shaping tool of FIG. 5A, according to theinvention.

FIG. 6 is a perspective view of wirebonding apparatus, including anotherembodiment of an external shaping tool, according to the invention.

FIG. 6A is a side view of a method of shaping an elongate element (e.g.,wire) with the shaping tool of FIG. 6, including a feature of theshaping tool for nicking or severing the elongate element, according tothe invention.

FIG. 6B is a side view of an elongate element that has been nicked todefine a series of shaped elongate elements which are linked end-to-end,according to the invention.

FIG. 7 is a side view of a technique for inserting a plurality of shapedelongate elements into a substrate, according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The disclosure of the aforementioned U.S. patent application Ser. Nos.08/452,255 and 08/573,945 are incorporated by reference herein. Thispatent application summarizes several of the techniques disclosedtherein.

An important aspect of the invention is that a composite interconnectionelement can be formed by starting with a core (which may be mounted to aterminal of an electronic component), then overcoating the core with anappropriate material to: (1) establish the mechanical properties of theresulting “composite” interconnection element; and/or (2) when theinterconnection element is mounted to a terminal of an electroniccomponent, securely anchor the interconnection element to the terminal.In this manner, a resilient interconnection element (spring element) canbe fabricated, starting with a core of a soft material which is readilyshaped into a springable shape and which is readily attached to even themost fragile of electronic components. In light of prior art techniquesof forming spring elements from hard materials, is not readily apparent,and is arguably counter-intuitive, that soft materials can form thebasis of spring elements. Such a “composite” interconnection element isgenerally the preferred form of resilient contact structure for use inthe embodiments of the invention.

FIGS. 1A, 1B, 1C and 1D illustrate, in a general manner, various shapesfor composite interconnection elements, according to the invention.

In the main, hereinafter, composite interconnection elements whichexhibit resiliency are described. However, it should be understood thatnon-resilient composite interconnection elements fall within the scopeof the invention.

Further, in the main hereinafter, composite interconnection elementsthat have a soft (readily shaped, and amenable to affixing by friendlyprocesses to electronic components) core, overcoated by hard (springy)materials are described. It is, however, within the scope of theinvention that the core can be a hard material—the overcoat servingprimarily to securely anchor the interconnection element to a terminalof an electronic component.

In FIG. 1A, an electrical interconnection element 110 includes a core112 of a “soft” material (e.g., a material having a yield strength ofless than 40,000 psi), and a shell (overcoat) 114 of a “hard” material(e.g., a material having a yield strength of greater than 80,000 psi).The core 112 is an elongate element shaped (configured) as asubstantially straight cantilever beam, and may be a wire having adiameter of 0.0005-0.0030 inches (0.001 inch=1 mil˜25 microns (μm ). Theshell 114 is applied over the already-shaped core 112 by any suitableprocess, such as by a suitable plating process (e.g., by electrochemicalplating).

FIG. 1A illustrates what is perhaps the simplest of spring shapes for aninterconnection element of the invention—namely, a straight cantileverbeam oriented at an angle to a force “F” applied at its tip 110 b. Whensuch a force is applied by a terminal of an electronic component towhich the interconnection element is making a pressure contact, thedownward (as viewed) deflection of the tip will evidently result in thetip moving across the terminal, in a “wiping” motion. Such a wipingcontact ensures a reliable contact being made between theinterconnection element and the contacted terminal of the electroniccomponent.

By virtue of its “hardness”, and by controlling its thickness(0.00025-0.00500 inches), the shell 114 imparts a desired resiliency tothe overall interconnection element 110. In this manner, a resilientinterconnection between electronic components (not shown) can beeffected between the two ends 110 a and 110 b of the interconnectionelement 110. (In FIG. 1A, the reference numeral 110 a indicates an endportion of the interconnection element 110, and the actual end oppositethe end 110 b is not shown.) In contacting a terminal of an electroniccomponent, the interconnection element 110 would be subjected to acontact force (pressure), as indicated by the arrow labelled “F”.

It is generally preferred that the thickness of the overcoat (whether asingle layer or a multi-layer overcoat) be thicker than the diameter ofthe wire being overcoated. Given the fact that the overall thickness ofthe resulting contact structure is the sum of the thickness of the coreplus twice the thickness of the overcoat, an overcoat having the samethickness as the core (e.g., 1 mil) will manifest itself, in aggregate,as having twice the thickness of the core.

The interconnection element (e.g., 110) will deflect in response to anapplied contact force, said deflection (resiliency) being determined inpart by the overall shape of the interconnection element, in part by thedominant (greater) yield strength of the overcoating material (versusthat of the core), and in part by the thickness of the overcoatingmaterial.

As used herein, the terms “cantilever” and “cantilever beam” are used toindicate that an elongate structure (e.g., the overcoated core 112) ismounted (fixed) at one end, and the other end is free to move, typicallyin response to a force acting generally transverse to the longitudinalaxis of the elongate element. No other specific or limiting meaning isintended to be conveyed or connoted by the use of these terms.

In FIG. 1B, an electrical interconnection element 120 similarly includesa soft core 122 (compare 112) and a hard shell 124 (compare 114). Inthis example, the core 122 is shaped to have two bends, and thus may beconsidered to be S-shpaed. As in the example of FIG. 1A, in this manner,a resilient interconnection between electronic components (not shown)can be effected between the two ends 120 a and 120 b of theinterconnection element 120. (In FIG. 1B, reference numeral 120 aindicates an end portion of the interconnection element 120, and theactual end opposite the end 120 b is not shown.) In contacting aterminal of an electronic component, the interconnection element 120would be subjected to a contact force (pressure), as indicated by thearrow labelled “F”.

In FIG. 1C, an electrical interconnection element 130 similarly includesa soft core 132 (compare 112) and a hard shell 134 (compare 114). Inthis example, the core 132 is shaped to have one bend, and may beconsidered to be U-shaped. As in the example of FIG. 1A, in this manner,a resilient interconnection between electronic components (not shown)can be effected between the two ends 130 a and 130 b of theinterconnection element 130. (In FIG. 1C, the reference numeral 130 aindicates an end portion of the interconnection element 130, and theactual end opposite the end 130 b is not shown.) In contacting aterminal of an electronic component, the interconnection element 130could be subjected to a contact force (pressure), as indicated by thearrow labelled “F”. Alternatively, the interconnection element 130 couldbe employed to make contact at other than its ends 130 b, as indicatedby the arrow labelled “F′”.

FIG. 1D illustrates another embodiment of a resilient interconnectionelement 140 having a soft core 142 and a hard shell 144. In thisexample, the interconnection element 140 is essentially a simplecantilever (compare FIG. 1A), with a curved tip 140 b, subject to acontact force “F” acting transverse to its longitudinal axis.

FIG. 1E illustrates another embodiment of a resilient interconnectionelement 150 having a soft core 152 and a hard shell 154. In thisexample, the interconnection element 150 is generally “C-shaped”,preferably with a slightly curved tip 150 b, and is suitable for makinga pressure contact as indicated by the arrow labelled “F”.

It should be understood that the soft core can readily be formed intoany springable shape—in other words, a shape that will cause a resultinginterconnection element to deflect resiliently in response to a forceapplied at its tip. For example, the core could be formed into aconventional coil shape. However, a coiled shape would not be preferred,due to the overall length of the interconnection element and inductances(and the like) associated therewith and the adverse effect of same oncircuitry operating at high frequencies (speeds).

The material of the shell, or at least one layer of a multi-layer shell(described hereinbelow) has a significantly higher yield strength thanthe material of the core. Therefore, the shell overshadows the core inestablishing the mechanical characteristics (e.g., resiliency) of theresulting interconnection structure. Ratios of shell:core yieldstrengths are preferably at least 2:1, including at least 3:1 and atleast 5:1, and may be as high as 10:1. It is also evident that theshell, or at least an outer layer of a multi-layer shell should beelectrically conductive, notably in cases where the shell covers the endof the core. (The parent case, however, describes embodiments where theend of the core is exposed, in which case the core must be conductive.)

From an academic viewpoint, it is only necessary that the springing(spring shaped) portion of the resulting composite interconnectionelement be overcoated with the hard material. From this viewpoint, it isgenerally not essential that both of the two ends of the core beovercoated. As a practical matter, however, it is preferred to overcoatthe entire core. Particular reasons for and advantages accruing toovercoating an end of the core which is anchored (attached) to anelectronic component are discussed in greater detail hereinbelow.

Suitable materials for the core (112, 122, 132, 142) include, but arenot limited to: gold, aluminum, copper, and their alloys. Thesematerials are typically alloyed with small amounts of other metals toobtain desired physical properties, such as with beryllium, cadmium,silicon, magnesium, and the like. It is also possible to use silver,palladium, platinum; metals or alloys such as metals of the platinumgroup of elements. Solder constituted from lead, tin, indium, bismuth,cadmium, antimony and their alloys can be used.

Vis-a-vis attaching an end of the core (wire) to a terminal of anelectronic component (discussed in greater detail hereinbelow),generally, a wire of any material (e.g., gold) that is amenable tobonding (using temperature, pressure and/or ultrasonic energy to effectthe bonding) would be suitable for practicing the invention. It iswithin the scope of this invention that any material amenable toovercoating (e.g., plating), including non-metallic material, can beused for the core.

Suitable materials for the shell (114, 124, 134, 144) include (and, asis discussed hereinbelow, for the individual layers of a multi-layershell), but are not limited to: nickel, and its alloys; copper, cobalt,iron, and their alloys; gold (especially hard gold) and silver, both ofwhich exhibit excellent current-carrying capabilities and good contactresistivity characteristics; elements of the platinum group; noblemetals; semi-noble metals and their alloys, particularly elements of theplatinum group and their alloys; tungsten and molybdenum. In cases wherea solder-like finish is desired, tin, lead, bismuth, indium and theiralloys can also be used.

The technique selected for applying these coating materials over thevarious core materials set forth hereinabove will, of course, vary fromapplication-to-application. Electroplating and electroless plating aregenerally preferred techniques. Generally, however, it would becounter-intuitive to plate over a gold core. According to an aspect ofthe invention, when plating (especially electroless plating) a nickelshell over a gold core, it is desirable to first apply a thin copperinitiation layer over the gold wire stem, in order to facilitate platinginitiation.

An exemplary interconnection element, such as is illustrated in FIGS.1A-1E may have a core diameter of approximately 0.001 inches and a shellthickness of 0.001 inches—the interconnection element thus having anoverall diameter of approximately 0.003 inches (i.e., core diameter plustwo times the shell thickness). Generally, this thickness of the shellwill be on the order of 0.2-5.0 (one-fifth to five times the thickness(e.g., diameter) of the core.

Some exemplary parameters for composite interconnection elements are:

(a) A gold wire core having a diameter of 1.5 mils is shaped to have anoverall height of 40 mils and a generally C-shaped curve (compare FIG.1E) of 9 mils radius, is plated with 0.75 mils of nickel (overalldiameter=1.5+2×0.75=3 mils), and optional receives a final overcoat of50 microinches of gold (e.g., to lower and enhance contact resistance).The resulting composite interconnection element exhibits a springconstant (k) of approximately 3-5 grams/mil. In use, 3-5 mils ofdeflection will result in a contact force of 9-25 grams. This example isuseful in the context of a spring element for an interposer.

(b) A gold wire core having a diameter of 1.0 mils is shaped to have anoverall height of 35 mils, is plated with 1.25 mils of nickel (overalldiameter=1.0+2×1.25=3.5 mils), and optionally receives a final overcoatof 50 microinches of gold. The resulting composite interconnectionelement exhibits a spring constant (k) of approximately 3 grams/mil, andis useful in the context of a spring element for a probe.

(c) A gold wire core having a diameter of 1.5 mils is shaped to have anoverall height of 20 mils and a generally S-shape curve with radii ofapproximately 5 mils, is plated with 0.75 mils of nickel or copper(overall diameter=1.5+2×0.75=3 mils). The resulting compositeinterconnection element exhibits a spring constant (k) of approximately2-3 grams/mil, and is useful in the context of a spring element formounting on a semiconductor device.

The core need not have a round cross-section, but may rather be a flattab (having a rectangular cross-section) extending from a sheet. Itshould be understood that, as used herein, the term “tab” is not to beconfused with the term “TAB” (Tape Automated Bonding).

MULTI-LAYER SHELLS

FIG. 2A illustrates an embodiment 200 of an interconnection element 210mounted to an electronic component 212 which is provided with a terminal214. In this example, a soft (e.g., gold) wire core 216 is bonded(attached) at one end 216 a to the terminal 214, is configured to extendfrom the terminal and have a spring shape (compare the shape shown inFIG. 1B), and is severed to have a free end 216 b. Bonding, shaping andsevering a wire in this manner is accomplished using wirebondingequipment. The bond at the end 216 a of the core covers only arelatively small portion of the exposed surface of the terminal 214.

A shell (overcoat) is disposed over the wire core 216 which, in thisexample, is shown as being multi-layered, having an inner layer 218 andan outer layer 220, both of which layers may suitable be applied byplating processes. One or more layers of the multi-layer shell is (are)formed of a hard material (such as nickel and its alloys) to impart adesired resiliency to the interconnection element 210. For example, theouter layer 220 may be of a hard material, and the inner layer may be ofa material that acts as a buffer or barrier layer (or as an activationlayer, or as an adhesion layer) in plating the hard material 220 ontothe core material 216. Alternatively, the inner layer 218 may be thehard material, and the outer layer 220 may be a material (such as softgold) that exhibits superior electrical characteristics, includingelectrical conductivity and solderability. When a solder or braze typecontact is desired, the outer layer of the interconnection element maybe lead-tin solder or gold-tin braze material, respectively.

ANCHORING TO A TERMINAL

FIG. 2A illustrates, in a general manner, another key feature of theinvention—namely, that resilient interconnection element can be securelyanchored to a terminal on an electronic component. The attached end 210a of the interconnection element will be subject to significantmechanical stress, as a result of a compressive force (arrow “F”)applied to the free end 210 b of the interconnection element.

As illustrated in FIG. 2A, the overcoat (218, 220) covers not only thecore 216, but also the entire remaining (i.e., other than the bond 216a)exposed surface of the terminal 214 adjacent the core 216 in acontinuous (non-interrupted) manner. This securely and reliably anchorsthe interconnection element 210 to the terminal, the overcoat materialproviding a substantial (e.g., greater that 50%) contribution toanchoring the resulting interconnection element to the terminal.Generally, it is only required that the overcoat material cover at leasta portion of the terminal adjacent the core. It is generally preferred,however, that the overcoat material cover the entire remaining surfaceof the terminal. Preferably, each layer of the shell is metallic.

As a general proposition, the relatively small area at which the core isattached (e.g., bonded) to the terminal is not well suited toaccommodating stresses resulting from contact forces (“F”) imposed onthe resulting composite interconnection element. By virtue of the shellcovering the entire exposed surface of the terminal (other than in therelatively small area comprising the attachment of the core end 216 a tothe terminal), the overall interconnection structure is firmly anchoredto the terminal. The adhesion strength, and ability to react contactforces, of the overcoat will far exceed that of the core end (216 a)itself.

As used herein, the term “electronic component” (e.g., 212) includes,but is not limited to: interconnect and interposer substrates;semiconductor wafers and dies, made of any suitable semiconductingmaterial such as silicon (Si) or gallium-arsenide (GaAs); productioninterconnect sockets; test sockets; sacrificial members, elements andsubstrates, as described in the parent case; semiconductor packages,including ceramic and plastic packages, and chip carriers; andconnectors.

The interconnection element of the invention is particularly well suitedfor use as:

interconnection elements mounted directly to silicon dies, eliminatingthe need for having a semiconductor package;

interconnection elements extending as probes from substrates (describedin greater detail hereinbelow) for testing electronic components; and

interconnection elements of interposers (discussed in greater detailhereinbelow).

The interconnection element of the invention is unique in that itbenefits from the mechanical characteristics (e.g., high yield strength)of a hard material without being limited by the attendant typically poorbonding characteristic of hard materials. As elaborated upon in theparent case, this is made possible largely by the fact that the shell(overcoat) functions as a “superstructure” over the “falsework” of thecore, two terms which are borrowed from the milieu of civil engineering.This is very different from plated interconnection elements of the priorart wherein the plating is used as a protective (e.g., anti-corrosive)coating, and is generally incapable of imparting the desired mechanicalcharacteristic to the interconnection structure. And this is certainlyin marked contrast to any non-metallic, anticorrosive coatings, such asbenzotriazole (BTA) applied to electrical interconnects.

Among the numerous advantages of the invention are that a plurality offree-standing interconnect structures are readily formed on substrates,from different levels thereof such as a PCB having a decouplingcapacitor) to a common height above the substrate, so that their freeends are coplanar with one another. Additionally, both the electricaland mechanical (e.g., plastic and elastic) characteristics of aninterconnection element formed according to the invention are readilytailored for particular applications. For example, it may be desirablein a given application that the interconnection elements exhibit bothplastic and elastic deformation. (Plastic deformation may be desired toaccommodate gross non-planarities in components being interconnected bythe interconnection elements.) When elastic behavior is desired, it isnecessary that the interconnection element generate a threshold minimumamount of contact force to effect a reliable contact. It is alsoadvantageous that the tip of the interconnection element makes a wipingcontact with a terminal of an electronic component, due to theoccasional presence of contaminant films on the contacting surfaces.

As used herein, the term “resilient”, as applied to contact structures,implies contact structures (interconnection elements) that exhibitprimarily elastic behavior in response to an applied load (contactforce), and the term “compliant” implies contact structures(interconnection elements) that exhibit both elastic and plasticbehavior in response to an applied load (contact force). As used herein,a “compliant” contact structure is a “resilient” contact structure. Thecomposite interconnection elements of the invention are a special caseof either compliant or resilient contact structures.

A number of features are elaborated upon in detail, in the parent case,including, but not limited to: fabricating the interconnection elementson sacrificial substrates; gang-transferring a plurality ofinterconnection elements to an electronic component; providing theinterconnection elements with contact tips, preferably with a roughsurface finish; employing the interconnection elements on an electroniccomponent to make temporary, then permanent connections to theelectronic component; arranging the interconnection elements to havedifferent spacing at their one ends than at their opposite ends;fabricating spring clips and alignment pins in the same process steps asfabricating the interconnection elements; employing the inconnectionelements to accommodate differences in thermal expansion betweenconnected components; eliminating the need for discrete semiconductorpackages (such as for SIMMs); and optionally soldering resilientinterconnection elements (resilient contact structures).

CONTROLLED IMPEDANCE

FIG. 2B shows a composite interconnection element 220 having multiplelayers. An innermost portion (inner elongate conductive element) 222 ofthe interconnection element 220 is either an uncoated core or a corewhich has been overcoated, as described hereinabove. The tip 222 b ofthe innermost portion 222 is masked with a suitable masking material(not shown). A dielectric layer 224 is applied over the innermostportion 222 such as by an electrophoretic process. An outer layer 226 ofa conductive material is applied over the dielectric layer 224.

In use, electrically grounding the outer layer 226 will result in theinterconnection element 220 having controlled impedance. An exemplarymaterial for the dielectric layer 224 is a polymeric material, appliedin any suitable manner and to any suitable thickness (e.g., 0.1-3.0mils).

The outer layer 226 may be multi-layer. For example, in instanceswherein the innermost portion 222 is an uncoated core, at least onelayer of the outer layer 226 is a spring material, when it is desiredthat the overall interconnection element exhibit resilience.

ALTERING PITCH

FIG. 2C illustrates an embodiment 250 wherein a plurality (six of manyshown) of interconnection elements 251 . . . 256 are mounted on asurface of an electronic component 260, such as a probe card insert (asubassembly mounted in a conventional manner to a probe card). Terminalsand conductive traces of the probe card insert are omitted from thisview, for illustrative clarity. The attached ends 251 a . . . 256 a ofthe interconnection elements 251 . . . 256 originate at a first pitch(spacing), such as 0.050-0.100 inches. The interconnection elements 251. . . 256 are shaped and/or oriented so that their free ends (tips) areat a second, finer pitch, such as 0.005-0.010 inches. An interconnectassembly which makes interconnections from a one pitch to another pitchis typically referred to as a “space transformer”.

As illustrated, the tips 251 b . . . 256 b of the interconnectionelements are arranged in two parallel rows, such as for making contactto (for testing and/or burning in) a semiconductor device having twoparallel rows of bond pads (contact points). The interconnectionelements can be arranged to have other tip patterns, for making contactto electronic components having other contact point patterns, such asarrays.

Generally, throughout the embodiments disclosed herein, although onlyone interconnection element may be shown, the invention is applicable tofabricating a plurality of interconnection components and arranging theplurality of interconnection elements in a prescribed spatialrelationship with one another, such as in a peripheral pattern or in arectangular array pattern.

USE OF SACRIFICIAL SUBSTRATES

The mounting of interconnection elements directly to terminals ofelectronic components has been discussed hereinabove. Generallyspeaking, the interconnection elements of the invention can befabricated upon, or mounted to, any suitable surface of any suitablesubstrate, including sacrificial substrates.

Attention is directed to the PARENT CASE, which describes, for examplewith respect to FIGS. 11A-11F fabricating a plurality of interconnectionstructures (e.g., resilient contact structures) as separate and distinctstructures for subsequent mounting to electronic components, and whichdescribes with respect to FIGS. 12A-12C mounting a plurality ofinterconnection elements to a sacrificial substrate (carrier) thentransferring the plurality of interconnection elements en masse to anelectronic component.

FIGS. 2D-2F illustrate a technique for fabricating a plurality ofinterconnection elements having preformed tip structures, using asacrificial substrate.

FIG. 2D illustrates a first step of the technique 250, in which apatterned layer of masking material 252 is applied onto a surface of asacrificial substrate 254. The sacrificial substrate 254 may be of thin(1-10 mil) copper or aluminum foil, by way of example, and the maskingmaterial 252 may be common photoresist. The masking layer 252 ispatterned to have a plurality (three of many shown) of openings atlocations 256 a, 256 b, 256 c whereat it is desired to fabricateinterconnection elements. The locations 256 a, 256 b and 256 c are, inthis sense, comparable to the terminals of an electronic component. Thelocations 256 a, 256 b and 256 c are preferably treated at this stage tohave a rough or featured surface texture. As shown, this may beaccomplished mechanically with an embossing tool 257 forming depressionsin the foil 254 at the locations 256 a, 256 b and 256 c. Alternatively,the surface of the foil at these locations can be chemically etched tohave a surface texture. Any technique suitable for effecting thisgeneral purpose is within the scope of this invention, for example sandblasting, peening and the like.

Next, a plurality (one of many shown) of conductive tip structures 258are formed at each location (e.g., 256 b), as illustrated by FIG. 2E.This may be accomplished using any suitable technique, such aselectroplating, and may include tip structures having multiple layer ofmaterial. For example, the tip structure 258 may have a thin (e.g.,10-100 microinch) barrier layer of nickel applied onto the sacrificialsubstrate, followed by a thin (e.g., 10 microinch) layer of soft gold,followed by a thin (e.g., 20 microinch) layer of hard gold, followed bya relatively thick (e.g., 200 microinch) layer of nickel, followed by afinal thin (e.g., 100 microinch) layer of soft gold. Generally, thefirst thin barrier layer of nickel is provided to protect the subsequentlayer of gold from being “poisoned” by the material (e.g., aluminum,copper) of the substrate 254, the relatively thick layer of nickel is toprovide strength to the tip structure, and the final thin layer of softgold provides a surface which is readily bonded to. The invention is notlimited to any particulars of how the tip structures are formed on thesacrificial substrate, as these particulars would inevitably vary fromapplication-to-application.

As illustrated by FIG. 2E, a plurality (one of many shown) of cores 260for interconnection elements may be formed on the tip structures 258,such as by any of the techniques of bonding a soft wire core to aterminal of an electronic component described hereinabove. The cores 260are then overcoated with a preferably hard material 262 in the mannerdescribed hereinabove, and the masking material 252 is then removed,resulting in a plurality (three of many shown) of free-standinginterconnection elements 264 mounted to a surface of the sacrificialsubstrate, as illustrated by FIG. 2F.

In a manner analogous to the overcoat material covering at least theadjacent area of a terminal (214) described with respect to FIG. 2A, theovercoat material 262 firmly anchors the cores 260 to their respectivetip structures 258 and, if desired, imparts resilient characteristics tothe resulting interconnection elements 264. As noted in the PARENT CASE,the plurality of interconnection elements mounted to the sacrificialsubstrate may be gang-transferred to terminals of an electroniccomponent. Alternatively, two widely divergent paths may be taken.

It is within the scope of this invention that a silicon wafer can beused as the sacrificial substrate upon which tip structures arefabricated, and that tip structures so fabricated may be joined (e.g.,soldered, brazed) to resilient contact structures which already havebeen mounted to an electronic component.

As illustrated by FIG. 2G, the sacrificial substrate 254 may simply beremoved, by any suitable process such as selective chemical etching.Since most selective chemical etching processes will etch one materialat a much greater rate than an other material, and the other materialmay slightly be etched in the process, this phenomen is advantageouslyemployed to remove the thin barrier layer of nickel in the tip structurecontemporaneously with removing the sacrificial substrate. However, if aneed be, the thin nickel barrier layer can be removed in a subsequentetch step. This results in a plurality (three of many shown) ofindividual, discrete, singulated interconnection elements 264, asindicated by the dashed line 266, which may later be mounted (such as bysoldering or brazing) to terminals on electronic components.

It bears mention that the overcoat material may also be slightly thinnedin the process of removing the sacrificial substrate and/or the thinbarrier layer. However, it is preferred that this not occur.

To prevent thinning of the overcoat, it is preferred that a thin layerof gold or, for example, approximately 10 microinches of soft goldapplied over approximately 20 microinches of hard gold, be applied as afinal layer over the overcoat material 262. Such as outer layer of goldis intended primarily for its superior conductivity, contact resistance,and solderability, and is generally highly impervious to most etchingsolutions contemplated to be used to remove the thin barrier layer andthe sacrificial substrate.

Alternatively, as illustrated by FIG. 2H, prior to removing thesacrificial substrate 254, the plurality (three of many shown) ofinterconnection elements 264 may be “fixed” in a desired spatialrelationship with one another by any suitable support structure 266,such as by a thin plate having a plurality of holes therein, whereuponthe sacrificial substrate is removed. The support structure 266 may beof a dielectric material, or of a conductive material overcoated with adielectric material. Further processing steps (not illustrated) such asmounting the plurality of interconnection elements to an electroniccomponent such as a silicon wafer or a printed circuit board may thenproceed. Additionally, in some applications, it may be desirable tostabilize the tips (opposite the tip structures) of the interconnectionelements 264 from moving, especially when contact forces are appliedthereto. To this end, it may also be desirable to constrain movement ofthe tips of the interconnection elements with a suitable sheet 268having a plurality of holes, such as mesh formed of a dielectricmaterial.

A distinct advantage of the technique 250 described hereinabove is thattip structures (258) may be formed of virtually any desired material andhaving virtually any desired texture. As mentioned hereinabove, gold isan example of a noble metal that exhibits excellent electricalcharacteristics of electrical conductivity, low contact resistance,solderability, and resistance to corrosion. Since gold is alsomalleable, it is extremely well-suited to be a final overcoat appliedover any of the interconnection elements described herein, particularlythe resilient interconnection elements described herein. Other noblemetals exhibit similar desirable characteristics. However, certainmaterials such as rhodium which exhibit such excellent electricalcharacteristics would generally be inappropriate for overcoating anentire interconnection element. Rhodium, for example, is notabllybrittle, and may not perform well as a final overcoat on a resilientinterconnection element. In this regard, techniques exemplified by thetechnique 250 readily overcome this limitation. For example, the firstlayer of a multi-layer tip structure (see 258) can be rhodium (ratherthan gold, as described hereinabove), thereby exploiting its superiorelectrical characteristics for making contact to electronic componentswithout having any impact whatsoever on the mechanical behavior of theresulting interconnect element.

FIG. 2I illustrates an alternate embodiment 270 for fabricatinginterconnection elements. In this embodiment, a masking material 272 isapplied to the surface of a sacrificial substrate 274, and is patternedto have a plurality (one of many shown) of openings 276, in a mannersimilar to the technique described hereinabove with respect to FIG. 2D.The openings 276 define areas whereat interconnection elements will befabricated as free-standing structures. (As used throughout thedescriptions set forth herein, an interconnection element is“free-standing” when is has a one bonded to a terminal of an electroniccomponent or to an area of a sacrificial substrate, and the opposite endof the interconnection element is not bonded to the electronic componentor sacrificial substrate.)

The area within the opening may be textured, in any suitable manner,such as to have one or more depressions, as indicated by the singledepression 278 extending into the surface of the sacrificial substrate274.

A core (wire stem) 280 is bonded to the surface of the sacrificialsubstrate within the opening 276, and may have any suitable shape. Inthis illustration, only a one end of one interconnection element isshown, for illustrative clarity. The other end (not shown) may beattached to an electronic component. It may not readily be observed thatthe technique 270 differs from the aforementioned technique 250 in thatthe core 280 is bonded directly to the sacrificial substrate 274, ratherthan to a tip structure 258. By way of example, a gold wire core (280)is readily bonded, using conventional wirebonding techniques, to thesurface of an aluminum substrate (274).

In a next step of the process (270), a layer 282 of gold is applied(e.g., by plating) over the core 280 and onto the exposed area of thesubstrate 274 within the opening 276, including within the depression278. The primary purpose of this layer 282 is to form a contact surfaceat the end of the resulting interconnection element (i.e., once thesacrificial substrate is removed).

Next, a layer 284 of a relatively hard material, such as nickel, isapplied over the layer 282. As mentioned hereinabove, one primarypurpose of this layer 284 is to impart desired mechanicalcharacteristics (e.g., resiliency) to the resulting compositeinterconnection element. In this embodiment, another primary purpose ofthe layer 284 is to enhance the durability of the contact surface beingfabricated at the lower (as viewed) end of the resulting interconnectionelement. A final layer of gold (not shown) may be applied over the layer284, to enhance the electrical characteristics of the resultinginterconnection element.

In a final step, the masking material 272 and sacrificial substrate 274are removed, resulting in either a plurality of singulatedinterconnection elements (compare FIG. 2G) or in a plurality ofinterconnection elements having a predetermined spatial relationshipwith one another (compare FIG. 2H).

This embodiment 270 is exemplary of a technique for fabricating texturedcontact tips on the ends of interconnection elements. In this case, anexcellent example of a “gold over nickel” contact tip has beendescribed. It is, however, within the scope of the invention that otheranalogous contact tips could be fabricated at the ends ofinterconnection elements, according to the techniques described herein.Another feature of this embodiment 270 is that the contact tips areconstructed entirely atop the sacrificial substrate (274), rather thanwithin the surface of the sacrificial substrate (254) as contemplated bythe previous embodiment 250.

SHAPING THE CORE ELEMENT BY MOVING THE COMPONENT

FIG. 3, corresponds generally to FIG. 2 of the PARENT CASE, and is aperspective view of a wire, having had its free end bonded to asubstrate (which may be an electronic component), and configured to havea springable shape.

In this example, a wire 302 (compare 122, 132, 142, 152) has had itsfree ends 302 a bonded within a defined contact area 310 (which may be aterminal of an electronic component) on a surface 308 a of a substrate308, according to any of the techniques hereinabove. An initial positionof the capillary 304 is shown in dashed lines. A final position of thecapillary 304 is shown in solid lines. The surface 308 a of thesubstrate 308 lies in an x-y plane (although the overall surface of thesubstrate is not required to be planar). The final position of thecapillary 304 is shown in FIG. 3, in solid lines, as being displacedfrom the surface of the substrate in a positive z-direction. The wire302 is fed from a supply spool 306 through the capillary 304, and isconfigured (to have a shape) in the following manner.

The free (proximal) end 302 a of the wire 302 is bonded to the surface308 a of the substrate 308 at a point labelled “a”, with the capillary304 in its initial (dashed line) position. The capillary 304 is thenmoved along a trajectory of points, which are “generically” labelled“b”, “c”, and “d” in FIG. 3, to shape the wire in two or in threedimensions.

For the sake of descriptive clarity, movement of the capillary isdiscussed as indicative of relative motion between the substrate and thecapillary. Often, movements in the x- and y-directions are achieved bymoving the substrate (e.g., an x-y table to which the substrate ismounted), and movements in the z-direction are achieved by moving thecapillary. Generally, the capillary is usually oriented in the z-axis.However, it is within the scope of this invention that capillaries withmany degrees of freedom could be employed to configure the shape of thewire stem.

Generally, movement of the capillary 304 is effected by a positioningmechanism (POSN) 320 under the control of a microprocessor-basedcontroller (CONTROL) 322, and is linked to the capillary 304 by anysuitable linkage 324.

When the capillary has reached its final (solid line) position, the wire302 is severed. This is illustrated in FIG. 3 by an EFO (electronicflame off) electrode 332 positioned adjacent the capillary 304, theelectrode 332 receiving electrical energy from an electronic flame-off(EFO) circuit 334 which is operated under control of the controller 322.

As is discussed in the PARENT CASE, as well as in the aforementionedU.S. patent application Ser. No. 08/573,945, the operation of severingof the wire (e.g., by electronic flame-off) can be enhanced by providingultraviolet light directed at the cutoff position (position “d” in FIG.3) from an appropriate (e.g., ultraviolet) light source (not shown).

It is well known that the EFO electrode 332 can be moved towards andaway from the capillary 304 by means of actuators and linkages (notshown) under the direction of the control mechanism 322.

USING A SHAPING TOOL TO SHAPE THE CORE ELEMENT

Generally, in order to fabricate a composite interconnection element,one must start with a core element that is readily shaped to have aspringable shape. Inasmuch as it is preferred that the core element beof a material that is shapable, it is generally required to overcoatsuch an “inchoate” resilient structure to arrive at usable resilientcontact structure (composite interconnection element). The core elementis a “precursor” to the resulting composite interconnection element.

In the PARENT CASE, inter alia, certain improvements in wirebonding havebeen disclosed, such as providing ultrasonic energy during playing awire out of a capillary of a wirebonder and/or flowing gas through thecapillary to overcome stiction of the wire as it plays out of thecapillary. Overcoming these problems is substantially avoided by thepresent invention. Additionally, the phenomenon of stiction isadvantageously employed by the techniques of the present invention.

Generally, as described hereinabove, once the free (proximal) end of thewire has been bonded to the terminal, the capillary is moved generallyupward (in a z-axis direction) from the surface of the component uponwhich the terminal resides and the component, which typically is mountedto an x-y table (not shown) is moved in the x- and y-directions. Thisimparts a relative motion between the capillary and the component whichis suitably employed to shape the wire stem (core element). As thecapillary moves, the wire “plays out” of the end of the capillary, andthe relative motion between the capillary and the substrate iscontrolled, and imparts a desired shape to the wire.

Stiction of the wire as it plays out of the capillary is but one of theproblems that may be encountered when employing such techniques. Otherproblems include, drag in the capillary, speed, uniformity, and thelike.

According to the present invention, these difficulties can be overcomeby employing external (other than relative motion of the capillary)instrumentalities to shape the wire stem.

The concept of using an external tool to shape the wire stem can befound in the aforementioned commonly-owned U.S. Patent Applications, Forexample, in U.S. patent application Ser. No. 08/452,255 it is disclosedat page 260 that:

“It is within the scope of this invention that the shaping of the wirestem is augmented, or fully implemented by external means other than[relative] movement of the capillary.”

FIG. 4A illustrates a technique 400 of shaping an elongate element suchas a bond wire 402 (compare 302) that has already been bonded at one end402 a (compare 302 a) thereof, by a capillary of a wirebonder, to anarea of a substrate such as a terminal (shown as a dashed line area 410,compare 310) on a surface 408 a (compare 308 a) of an electroniccomponent 408 (compare 308), or at a position on any substrate,including a sacrificial substrate, including a position whereat a tipstructure has previously been formed. The wire 402 is supplied by asupply spool 406 (compare 306) of a wirebonder (not shown).

In FIG. 4A, the capillary 404 is shown as having been lifted (withdrawn)straight up (along the z-axis) off of the surface of the surface of thesubstrate so that a portion of the wire 402 extends in a substantiallystraight line between the component 408 and the tip (bottom end, asviewed) of the capillary 404, generally normal to the surface 408 a ofthe component 408.

For the purpose of forming an inchoate composite interconnectionelement, it is desired to shape this portion of the wire (elongateelement) between the capillary and the component to have a spring shape,for subsequent overcoating as described hereinabove. To achieve thispurpose, a shaping tool 412 is provided, and may conveniently beattached to the same linkage (mechanism, not shown) that moves the EFOelectrode 432 (compare 332) into and away from the capillary. The EFOelectrode 432 may be disposed upon the shaping tool 412, so that theymove in unison, or it may not.

The shaping tool 412 is in the form of an elongate element having ablunt front end (towards the left, in the figure). In this case, theblunt front end is semicircular. The shaping tool 412 has a thickness(into the page, as viewed in the figure) which is at least as great asthe thickness (diameter, in the case of a round wire) of the coreelement 402. Preferably, the thickness of the shaping tool is at leasttwice as large as the thickness of the core element.

After the end of the wire is bonded to the component, and the capillaryis withdrawn, the shaping tool 412 is urged against the wire,approximately at a midpoint between the component and the capillary, ina direction which is generally parallel to the surface of the component(in other words, generally transverse to the longitudinal axis of thewire). This results in the wire being deformed (shaped), as illustratedin FIG. 4B. In this example, the wire is shaped to have a shapecomparable to the shape shown in FIG. 1E, but any shape may be impartedto the wire in this manner. For example, two shaping tools could bebrought to bear upon the wire, from opposite sides of the wire, atdifferent longitudinal positions along the wire, to impart an S-likeshape to the wire.

Striction, mentioned hereinabove as being problematic when employingrelative movement of the capillary and the substrate to shape the wirestem, is advantageous to the technique of the present invention. Whenthe shaping tool is urged against the stretched-out portion of the wirebetween the capillary and the substrate, striction will provide arestraining force upon the wire further playing out the capillary,permitting the wire to acquire the desired shape.

After (at the conclusion of) shaping the wire in this manner, the EFOelectrode 432 may be activated to sever the wire from the capillary, asillustrated by the spark 414 between the EFO electrode 432 and the wire402. This results in a free-standing wire stem, as shown in FIG. 4C,which preferably has a ball formed at its free (top, as viewed in thefigure) end. Preferably, a ball is also formed at the end of the supplywire extending out of the capillary in preparation for making asubsequent wire bond to the component. The shaping tool 412 (and EFO, ifattached thereto) is then withdrawn, as illustrated by FIG. 4C.

Hence, a technique is provided for shaping a bond wire to serve as acore element of a composite interconnection element by use of anexternal instrumentality (i.e., a shaping tool) rather than by movingthe component (relative to the capillary) in the x- and y- directions.This is advantageous for the reasons stated above (overcoming striction,etc.), and may be necessary in order to form certain (e.g., fine pitch)arrays of wire stems for composite interconnection elements, dependingon the clearances between adjacent wire stems.

Preferably, the shaping tool (412) moves in the plane of the substrate408 (i.e., in the x or y axis), but it is permissible that there be adownward (towards the surface of the substrate) component of the motionof the shaping tool. Preferably, the tool does not move upward (towardsthe capillary, away from the substrate) as it is shaping the elongateelement (402), since this would tend to pull on the previously-formedbond.

It is within the scope of this invention that the shaping tool (412)perform functions in addition to shaping a played-out wire. For example,it can readily be utilized to bond a midportion of a wire stem toanother adjacent structure, such as a bore of a hole in a planar supportstructure. In such as case, after severing, the two ends of the shapedcore element would extend from the two opposite surfaces of the planarsupport structure, and the shaped elements would be retained therewith,in a fixed spatial relationship to one another.

Another Embodiment of a Shaping Tool

FIGS. 5A-5C illustrate another embodiment 500 of a technique for shapinga portion of an elongate element 502 extending between an area 510(compare 410) of a substrate 508 (compare 408), such as a terminal of anelectronic component, and a capillary 504 (compare 404) of a wirebonder(see FIG. 3). The elongate element 502 is suitably supplied by a supplyspool 506 (compare 406).

In this embodiment, as shown in FIG. 5A, the shaping tool 512 (compare412) is a rod (cylindrical element) that is moved in the x-y plane by anactuator (“ACT”) 520 such as a solenoid. The dashed line 522 between therod and the actuator signified any suitable linkage elements such aslevers. Preferably, the actuator 520 is of a type, the motion andposition of which can be controlled (e.g., by software), such as acombination motor/encoder or servo system, over its entire range ofmotion. In this manner, the force applied by the shaping tool to theelongate element and the travel of the shaping tool can be carefullycontrolled and profiled. It is within the scope of the invention,however, that a simple solenoid can be used as the actuator, the “throw”(distance that the solenoid moves) of the solenoid being limited by asuitable mechanical stop associated with the linkage (or, with theshaping tool itself).

The shaping tool 512 is preferably formed of a material which is harderthan the material of the elongate element 502, such as tungsten, quartz,or the like. It is within the scope of this invention that the shapingtool can be heated, such as with an excimer laser, to aid in shaping theelongate element. It is within the scope of this invention that anelectrical potential (including grounding) can be applied to the shapingtool for controlling a severing spark applied to the elongate element.

It is within the scope of the invention that the rod (512) is notched orgrooved (i.e., in a circumferential direction), to ensure that the wire(502) does not slip (e.g., back and forth along the rod) while the wireis being shaped.

FIG. 5B shows the shaping tool 512 being urged against the elongateelement 502, causing the elongate element to have a spring shape. FIG.5C shows the shaping tool having been withdrawn from the elongateelement 502, and the elongate element having been severed adjacent thecapillary 504.

In FIGS. 5B and 5C, the elongate element 502 is illustrated as havingbeen caused to have a shape similar to the shape shown in FIG. 1E (aC-shape). The diameter of the shaping tool 512 is preferably slightlyless that the final height of the shaped elongate element. For example,a shaped elongate element having height of 30-40 mils can beappropriately shaped by a cylindrical shaping tool having a diameter of20-25 mils. This is but one of many possible spring shapes that can beimparted to the elongate element.

Preferably, in the embodiment 500, the elongate element 502 is severedby a spark from an electronic flame off (EFO) electrode 532 (compare332) which is fixed with respect to the capillary 504 (rather thanmounted to the shaping tool as in the previously-described embodiment400).

It is within the scope of this invention that the elongate element issevered with a spark 514 (compare 414), while the shaping tool 512 is inmechanical and electrical contact (engagement) with the elongate element502, as illustrated in FIG. 5B. The shaping tool 512 could be grounded,or at a given potential to control the spark and/or to prevent the sparkfrom damaging a delicate electronic component (508). This would also beapplicable to the previously-described embodiment 400.

In the previously-described embodiments (400, 500) of using a shapingtool (412, 512) to impart a spring shape to the elongate element (e.g.,bond wire), the bond wire is first bonded to the substrate and thecapillary (404, 504) is withdrawn in the z-axis to feed out the portionof the bond wire which is desired to be shaped.

It is within the scope of this invention that a shaping tool can have aplurality of degrees of freedom, and may be moved in a manner that theelongate element twists around the shaping tool, to impart complexshapes to the shaped portion of the elongate element.

It is within the scope of the invention that the wire stem severed bymechanical means rather than by a spark.

Compound Shaping Tool

In the previously-described embodiments (400, 500) of the invention, theshaping tool (412, 512) deforms the elongate element (402, 502) in afairly controlled manner, relying solely on plastic deformation of theelongate element for the elongate element to retain its desired shape.Evidently, a limited amount of overtravel may be required to achieve thedesired shape, depending upon the material qualities of the elongateelement.

FIG. 6 illustrates an embodiment 600 using a two-part shaping tool toimpart a spring shape of an elongate element. This embodiment isparticularly useful for shaping elongate elements made of materials(e.g., spring materials) having a relatively high yield strength, suchas elongate elements that are capable of functioning as monolithicspring elements. As in the previous embodiments (400, 500), it isdesired to impart a spring shape to an elongate element 602 (compare402, 502) which may be (but need not be) bonded at one end to asubstrate 608 (compare 408, 508) and which is fed from a capillary 604(compare 404, 504).

A one part 622 of the two-part shaping tool 620 is an anvil, and anotherpart 624 of the two-part shaping tool 620 is a die (in the mechanicalsense). The anvil 622 and die 624 are positioned on opposite sides ofthe elongate element, and are operatively linked to suitable mechanisms(not shown) for bringing the two parts together (towards one another),as illustrated by the arrows in the figure.

The inner faces 622 a and 624 a of the anvil 622 and die 624, areprovided with matching mating convex and concave features 626 and 628,respectively. In use, when the anvil and die are brought together, theelongate element 602 acquires the shape of these features.

As in the previous embodiments (400, 500), the elongate element can besevered by a spark while one or both of the anvil and die are in contactwith the elongate element.

FIG. 6A illustrates an embodiment 650 of a two-part, “compound” shapingtool comprising an anvil 672 and a die 674 comparable to the previouslydescribed anvil and die 622 and 624, respectively.

In this embodiment 650, it is intended to shape and at least notch(nick) an end portion of an elongate element 652 (compare 602) which isnot mounted (at one end thereof) to a substrate and which may besupplied by any suitable means (i.e., other than a capillary of awirebonder). Completely severing the elongate element with the die/anvilis also a possibility. Controlling an electrostatic discharge from anEFO electrode to occur at the nick is also a possibility.

It is within the scope of the invention that a feature is incorporatedinto the capillary to perform a portion or all of the nicking function.With a wedge bonding tool, this would also be possible. Penetrating ahole (transverse to the bore) in the capillary with a notching tool isalso a possibility.

As in the previous embodiment (600), the anvil 672 is provided with aconvex feature 676 (compare 626) and the die is provided with a concavefeature 678 (compare 628) on their opposing faces so that a desiredshape can be imparted to the portion of the elongate element disposedbetween the die and anvil.

In addition to the above, at least one of the anvil 672 and die 674 isprovided with a projecting wedge-shaped feature which is sized andshaped to at least notch (including completely severing) the elongateelement. Preferably, both the anvil 672 and die 674 are provided withsuch features 682 and 684, respectively, as shown in the figure. In thismanner, when the anvil and the die are moved towards one another, withthe elongate element disposed therebetween, the elongate element is bothshaped and notched (optionally, completely severed). If completelysevered, a plurality of shaped elongate elements can be formed in thismanner. If only notched, a series of shaped elongate elements, connectedend-to-end, can be formed in this manner.

FIG. 6B illustrates a series of elongate elements 652 a, 652 b and 652c, connected end-to-end, separable (e.g., by flexing a one element withrespect to the remaining elements) from one another by notches 686 a(between elements 652 a and 652 b) and 686 b (between elements 652 b and652 c). The elongate elements 652 a, 652 b and 652 c may be shaped, withthe shaping tool of FIG. 6 (or of FIG. 6A). They are illustrated withoutsuch a shape, for illustrative clarity, but see FIG. 7, hereinbelow.

The nick regions 686 a and 686 b are of reduced cross-section. Whenusing a spark (electrical discharge) severing technique (such as from anEFO electrode), the spark severing will occur preferentially at the nickregions of reduced cross-section.

In order to merely notch the elongate element (i.e., as opposed tocompletely severing the elongate element), the aggregate height (acrossthe page) should be less than the thickness (or diameter, in the case ofa wire) of the elongate element.

FIG. 7 shows a technique 700 similar to the aforementioned technique offorming a series of shaped elongate elements (652 a, 652 b, 652 c) whichare connected end-to-end, wherein as each elongate element is formed, itis inserted into an area of a relatively soft substrate. In thisexample, the same anvil 672 and die 674 can be employed as in theprevious embodiment 600.

FIG. 7 illustrates an elongate element 702 (compare 652) being fed(downward, as viewed in the figure) through (between) the anvil 672 anddie 674. A first shaped elongate element 702 a is shown as havingalready been shaped and nicked by the anvil 672 and die 674. Anext-in-the-series elongate element 702 b is shown as being clampedbetween the anvil 672 and die 674. The end (bottom, as viewed in thefigure) of the first shaped element 702 a may then be inserted, such asby piercing, at a selected position, into or through a selected area ona relatively (relative to the elongate element) soft substrate 708(including a relatively hard substrate which is provided with relativelysoft areas). Then, by imparting relative motion between the substrate708 and the clamped next elongate element 702 b, the fist elongateelement 702 a can be separated (singulated) from the elongate element702. This process of shaping, piercing, moving (singulating) can berepeated at numerous locations on the substrate 708, in order to providea plurality of shaped elements (702 a, 702 b, etc.) at a like pluralityof locations on the relatively soft substrate 708, in any desiredpattern, such as in an array. In this manner, a plurality of shapedcontact elements can be formed and maintained in a defined spatialrelationship with one another, for future use (e.g., as an interposer)or processing (e.g., for overcoating the shaped elements).

For example, the elongate element 702 may be a hard copper or invarwire, the substrate may be a ceramic material with a plurality oflithographically defined areas of gold/tin (80/20), the tips of theshaped elements can be fluxed prior to inserting into the gold/tin areasof the substrate and reflow soldered after inserting into the gold tinareas of the substrate, and the like, and the entire array can be plated(overcoated) with gold or the like. A rigid backing plate 710 issuitably provided behind the soft substrate 708.

Alternatively, the shaped elongate elements can be inserted into platedthrough holes of substrates, including sacrificial substrates.

Although the invention has been illustrated and described in detail inthe drawings and foregoing description, the same is to be considered asillustrative and not restrictive in character—it being understood thatonly preferred embodiments have been shown and described, and that allchanges and modifications that come within the spirit of the inventionare desired to be protected. Undoubtedly, many other “variations” on the“themes” set forth hereinabove will occur to one having ordinary skillin the art to which the invention (including the present invention) mostnearly pertains, and such variations are intended to be within the scopeof the invention, as disclosed herein. Several of these variations areset forth in the PARENT CASE.

For example, a separate shaping tool can be used in conjunction withtechniques other than ball bonding, such as in conjunction with wedgebonding.

For example, the composite interconnection element of the invention canbe used as a spring contact for a variety of interposers, a springcontact on silicon, a spring contact having controlled impedance, etc.

For example, it is evidently possible to control the movements of thecapillary and the shaping tool so that they are coordinated, accordingto any desired schedule, with one another. For example, in the techniqueillustrated in FIGS. 5A-5C, the capillary can move down slightlyimmediately prior to urging the shaping tool against the played outwire, and can further be moved during the shaping operation, to ensurereliable spring shape formation.

For example, it is evident that the use of a die/anvil combination forshaping (see, e.g., FIGS. 6 and 7) may be difficult to use when it isdesired to form a plurality of free-standing spring-shaped elementswhich are mounted by their one ends to a substrate. It is within thescope of this invention that the capillary is moved in a manner to playout a length of wire (including ribbon-like wire), possibly temporarilysecuring the free end of wire (if necessary) to achieve thisplaying-out, moving the capillary out of the way (e.g., lifting thecapillary), shaping the played-out portion of the wire with thedie/anvil, then lowering the capillary. This is also exemplary of thecoordinated motions of the shaping tool and capillary that are readilyachieved with the present invention.

What is claimed is:
 1. The method of shaping a portion of an elongateelement extending away from an area of a substrate, comprising:providing a substrate with a surface and an area adjacent the surface ofthe substrate; forming an elongate element connected to and extendingfrom the substrate, the elongate element in a first shape; urging ashaping tool against the elongate element to impart a second shape to asecond portion of the elongate element; providing a bulk conductivematerial; forming the elongate element from the bulk conductivematerial; in conjunction with shaping the elongate element, severing theshaped elongate element from the bulk conductive material; and severingthe shaped elongate element from the bulk conductive material with aspark.
 2. The method, according to claim 1, further comprising:providing the spark by an electrode mounted to the shaping tool.
 3. Themethod, according to claim 1, further comprising: forming the elongateelement using a wirebonder including a capillary, wherein the spark isprovided by an electrode mounted in a fixed relationship to thecapillary.
 4. The method of shaping a portion of an elongate elementextending away from an area of a substrate, comprising: providing asubstrate with a surface and an area adjacent the surface of thesubstrate; forming an elongate element connected to and extending fromthe substrate, the elongate element in a first shape; urging a shapingtool against the elongate element to impart a second shape to a secondportion of the elongate element; and providing a cutting feature on theshaping tool, and severing the elongate element with the cutting featureon the shaping tool.
 5. The method of shaping a portion of an elongateelement extending away from an area of a substrate, comprising:providing a substrate with a surface and an area adjacent the surface ofthe substrate; forming an elongate element connected to and extendingfrom the substrate, the elongate element in a first shape; urging ashaping tool against the elongate element to impart a second shape to asecond portion of the elongate element; and forming the elongate elementusing a wirebonder including a capillary, and severing the elongateelement adjacent the capillary with a spark from an electrode.
 6. Themethod of shaping a portion of an elongate element extending away froman area of a substrate, comprising: providing a substrate with a surfaceand an area adjacent the surface of the substrate; forming an elongateelement connected to and extending from the substrate, the elongateelement in a first shape; urging a shaping tool against the elongateelement to impart a second shape to a second portion of the elongateelement; mounting a plurality of flexible elements to the surface of thesubstrate; shaping the flexible elements with the shaping tool; andovercoating each one of the plurality of the flexible elements with atleast one layer of at least one overcoating material.
 7. The methodaccording to claim 6, wherein the flexible elements comprise a firstmaterial; at least one layer of the overcoating material comprises asecond material, wherein the first material is soft relative to thesecond material.
 8. The method, according to claim 6, wherein: theovercoating material comprises a material selected from the groupconsisting of nickel and its alloys.
 9. The method, according to claim6, wherein the substrate is a sacrificial substrate, and furthercomprising removing the sacrificial substrate.
 10. The method of shapinga portion of an elongate element extending away from an area of asubstrate, comprising: providing a substrate with a surface and an areaadjacent the surface of the substrate; forming an elongate elementconnected to and extending from the substrate, the elongate element in afirst shape; urging a shaping tool against the elongate element toimpart a second shape to a second portion of the elongate element; andovercoating the elongate element with an overcoating material ofsufficient thickness and of sufficient yield strength to impart adesired amount of resiliency to the resulting composite interconnectionelement and to dominate said resiliency.
 11. The method, according toclaim 10, wherein: the flexible element has a first yield strength; theovercoating material has a second yield strength; and the second yieldstrength is at least twice the first yield strength.
 12. The method ofshaping a portion of an elongate element extending away from an area ofa substrate, comprising: providing a substrate with a surface and anarea adjacent the adjacent the surface of the substrate; forming anelongate element connected to and extending from the substrate, theelongate element in a first shape; urging a shaping tool against theelongate element to impart a second shape to a second portion of theelongate element; providing a terminal on the substrate, wherein thearea of the substrate is the terminal; and overcoating the elongateelement and at least an adjacent portion of the terminal with anovercoating material of sufficient thickness and of sufficient yieldstrength to securely mount the resulting composite interconnectionelement to the terminal, said overcoating material making a substantialcontribution to anchoring the overcoated elongate element to theterminal.
 13. The method of shaping a portion of an elongate elementextending away from an area of a substrate, comprising: providing asubstrate with a surface and an area adjacent the surface of thesubstrate; forming flexible, elongate element connected to and extendingfrom the substrate, the flexible, elongate element in a first shape;urging a shaping tool against the elongate element to impart a secondshape to the flexible, elongate element; and overcoating the flexible,elongate element with at least one layer of at least one overcoatingmaterial.